1. Technical Field
The present disclosure relates to an optical plate, a backlight assembly having the optical plate, and a display device having the optical plate. More particularly, the present disclosure relates to an optical plate for improving light efficiency, a backlight assembly having the optical plate, and a display device having the optical plate.
2. Discussion of the Related Art
In general, a backlight assembly employed in a liquid crystal display (LCD) device has an important influence on the brightness, appearance, etc., of the image on the LCD device. The backlight assembly typically includes a lamp assembly, a light-guiding plate or a diffusion plate assembly, a housing unit, etc.
Particularly, a backlight assembly employed in an LCD TV has a structure that includes a diffusion plate, a diffusion sheet and a luminance-enhancing sheet that are sequentially stacked. Since light passes through various media, which have different refractive indexes, in the structure of the backlight assembly, a transfer of energy occurs so that a large amount of the light produced by the lamp of the lamp assembly is lost.
Moreover, since many optical sheets are used in the structure and mounting treatment of the optical sheets becomes very difficult. Further, the cost of manufacturing the complicated backlight assembly is increased.
FIG. 1 is a cross sectional view illustrating light paths in a backlight assembly having a conventional diffusion plate.
Referring to FIG. 1, a conventional diffusion plate 2 is arranged over a plurality of lamps 4 that are arranged in parallel. The diffusion plate 2 diffuses light emitted from the lamps 4 and light reflected from a reflection plate 6. The diffusion plate 2 then irradiates the light in an upward direction. Here, bright lines and dark lines may be generated in a surface portion of the diffusion plate 2 corresponding to the lamps 4. Particularly, the bright lines are generated in regions I of the diffusion plate 2 relatively adjacent to the lamps 4. In contrast, the dark lines are generated in regions II of the diffusion plate 2 relatively distant from the lamps 4.
The bright lines and the dark lines may vary in accordance with a thickness and efficiency of the diffusion plate 2. That is, light transmissivity of the diffusion plate 2 is improved and luminance uniformity of the diffusion plate 2 is decreased in proportion to reducing the thickness of the diffusion plate 2. In contrast, the light transmissivity of the diffusion plate 2 is decreased and the luminance uniformity of the diffusion plate 2 is improved in proportion to increasing the thickness of the diffusion plate 2. These are caused by an increase of diffusion distribution and by an increase of light loss of the lamp in proportion to a scattering of the light paths.
To remove the bright lines and the dark lines, optical sheets are arranged over the diffusion plate or the space between the lamp and the diffusion plate is widened. However, the arrangement of the optical sheets and the widening of the spacing cause an increase in a thickness of an LCD module. Thus, one or two additional diffusion sheets are arranged to remove the bright lines and the dark lines. However, the additional diffusion sheets cause an increase in the costs of manufacturing the backlight assembly.
Further, the light efficiency of the conventional backlight assembly may be reduced in proportion to an increase of the light loss.